The Roman section only
of an article by Robert Whiston, M.A., Fellow of Trinity College, Cambridge
on pp240‑241 of

CARCER
(kerker, German; γοργύρα, Greek), a prison. This word is connected with ἕρκος and εἵργω, the guttural being interchanged with the aspirate.

[. . .]

2. Roman.—
A carcer, or prison, was first built at Rome by Ancus Martius, overhanging the forum
(Liv. I.33). This was enlarged by Servius Tullius, who added to it a souterrain, or dungeon, called from him the
Tullianum. Sallust
(Cat. 55)
describes this as being twelve feet under ground, walled on each side, and arched over with stone work. For a long time it was the only prison at Rome
(Juv. Sat.III.312), being, in fact, the "Tower," or state prison of the city, which was sometimes doubly guarded in times of alarm, and was the chief object of attack in many conspiracies (Liv.
XXVI.27,
XXXII.26). Varro (L. L.V.151, ed. Müller) tells us that the Tullianum was also named "Lautumiae," from some quarries in the neighbourhood; or, as others think in allusion to the "Lautumiae" of Syracuse, a prison cut out of the solid rock. In later times the whole building was called the "Mamertine." Close to it were the
Scalae Gemoniae, or steps, down which the bodies of those who had been executed were thrown into the Forum, to be exposed to the gaze of the Roman populace (Cramer, Ancient Italy, vol. 1 p430). There were, however, other prisons besides this, though, as we might expect, the words of Roman historians generally refer to this alone. One of these was built by Appius Claudius, the decemvir, and in it he was himself put to death (III.57;
Plin. H. N.VII.36).

The carcer of which we are treating, was chiefly used as a place of confinement for persons under
p241 accusation, till the time of trial; and also as a place of execution, to which purpose the Tullianum was specially devoted. Thus, Sallust (l.c.) tells us that Lentulus, an accomplice of Catiline, was hanged there. Livy also
(XXIX.22)
speaks of a conspirator being delegatus in Tullianum, which in another passage
(XXXIV.44), is otherwise expressed by the words in inferiorem demissus carcerem, necatusque.

The same part of the prison was also called "robur," if we may judge from the words of Festus:— Robur in carcere dicitur is locus, quo praecipitatur maleficorum genus. This identity is further shown by the use made of it; for it is spoken of as a place of execution in the following passages:— In robore et tenebris exspirare (Liv.
XXXVIII.59; Sallust, l.c.). Robur et saxum (sc. Tarpeium) minitari
(Tacit. Ann.IV.29). So also we read of the catenas — et Italum robur
(Hor. Carm.II.13.18).

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